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SB tig braze help

10-11-2013, 02:42 PM

I am trying to repair a door from a wood stove from the shop. The frame looks to be brass and the inside is mild steel. Cleaned everything up and planned to tig braze with silicon bronze filler. Ran a test piece on mild steel and ran fine. Tried on my project and it doesn't stick to what I thought was the brass.

Using my cst280 in lift tig mode at 100 amps tri-mix tungsten and dcen. I tried between 75 and 125 amps and all the same result. What am I doing wrong? I have some pictures attached.

There is a lot of rust on the steel but I cleaned it up along the brazed section and also ground down to fresh metal on the bronze.

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Got a lot of heat into the bronze to make a puddle and it started turning white and pitting out. Good gas coverage and a gas lens. I am still not sure it is bronze. Just a guess. Silicon bronze tig brazing isn't supposed to melt the base metal. Just the filler. Much less heat input that way.

MillerMatic 251
Maxstar 150 STH
Cutmaster 42
Victor Journeyman OA

A rockcrawler, er money pit, in progress...

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Are you replacing a glass with steel? Have you ground the "bronze" to see that it is not white metal and plated, though it is not a place I would use white metal I'd have used cast iron but I can. I'd still get out the drill and bolt it.This would also let it work the steel and the "bronze independently as whatever it is it likely doesn't have the same co-efficient of expansion as the steel.---Meltedmetal

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This had mild steel glued on somehow and it fell out. I acquired this and just want to warm the shop with it. Might have had glass before. I ground a good layer off and it is definitely not white metal.

Steve-

Good to know about bronze. Why won't the sb melt to the bronze? This is my first time working with this metal. I like steel better!

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I checked some sources and it looks like you should use argon or argon/helium mixture. You could even use pure helium if your welding a thick part. The trick is too get a puddle started and keep the arc in the puddle moving it forward when you add the next drop of silicon bronze. Do not focus the arc just on the brass. If the brass gets too hot the zinc in the brass will migrate out at you with a pop and a white hazardous smoke. Use DC and pulse of about 30 and background about 50% if you have the pulse option on your machine. You could also braze this project with a gas torch. Hope this helps. Have fun!